A digital data storage system can include a hard disk drive (HDD) that stores data on storage media such as magnetic or optical data storage disks. In magnetic disk storage systems, the hard disk drive includes at least one hard disk in the form of a rigid platter, a head assembly for reading and writing data on the platter, and a controller for controlling the head assembly.
During a “read” or “write” operation, the head assembly scans the hard disk platter surface. The read/write head inside the head assembly is conventionally driven by a voice coil motor (VCM) and generally supported by an actuator arm for reading data from or writing data to a desired track on the platter. When current is fed to the VCM, the VCM develops force or torque which is substantially proportional to the applied current. The arm acceleration is therefore substantially proportional to the magnitude of the current. When the read/write head is near the desired track, a reverse polarity signal can be applied to the actuator arm, causing the read/write head to stop directly over the desired track.
Modern HDD throughput and storage capacity have been substantially enhanced by improvement in actuator design which has resulted in increased precision and speed in head placement. The more precisely and quickly the actuator arm can place the read/write head, the greater the amount of data that can be packed onto a given area of disk surface and the quicker such data can be accessed. The demand for increased speed and storage capacity has resulted in ever faster and more compact hard disk drive assemblies. Because speed is one of the dominant factors in determining the overall hard drive performance, conventional technologies have focused heavily on maximizing speed. However, the increase in speed frequently comes at the expense of head precision, producing undesirable errors and causing unrecoverable data.